This invention relates to a brush holder used for rotary electric machines such as generators or motors.
FIGS. 1(A) and 1(B) show a conventional brush holder, wherein FIG. 1(A) illustrates a brush which is not yet worn, and FIG. 1(B) illustrates a brush which is worn to a wearing limit. In FIGS. 1(A) and 1(B), numeral 1 designates a brush, numeral 2 a holder body which holes the brush 1 and which is composed of a brush frame 3 and a holder arm 4. Numeral 5 indicates a buruh retainer which is pivotally secured via a pin 5a to the holder arm 4 for retaining the brush 1 and which is composed of a lever 6 and a presser 7. Numeral 8 shows a spring utilized for applying pressure on brushes 1 by the brush retainer 5. The spring 8 is engaged at one end with a pin 10 which is provided on the lever 6 of the brush retainer 5 through a supporting bracket 9 and is engaged at the other end with a pin 11 which is provided on the holder arm 4 of the holder body 2. Numeral 12 denotes a stopper which is provided on the holder body 2 and which prevents the movement of the brush retainer 5 from going beyond a predetermined position. The stopper 12 is constructed to stop the movement of the brush retainer 5 when the brush 1 reaches its wearing limit.
However, in the conventional brush holder thus constructed as described above, the wear of the brush 1 is visually examined, and has the disadvantage that periodic checking is required to check the state of the brushes.